The present invention relates to new antibiotics, which we have called "chloropolysporins B and C", to a process for their preparation by the cultivation of a microorganism and to their use, both therapeutic, in the treatment and prophylaxis of infections caused by bacteria, and as a growth-promoting agent for animals.
As resistance to conventional antibiotics becomes increasingly established in common strains of pathogenic bacteria, the need for a wider variety of antibiotics for use in the fight against such bacteria becomes ever more crucial. Moreover, various antibiotics, for example chloramphenicol, aureomycin, vancomycin and avoparcin, have been administered, or have been proposed for administration, to poultry and other farm animals, including the ruminants and pigs, for the prophylaxis of disease or to promote growth or milk production. However, an inherent disadvantage of the use of antibiotics in this way is that there is some risk that traces of the antibiotics or of metabolic products thereof may be found in animal products intended for human consumption (such as eggs, milk or meat); the alleged dangers of such residues are increasingly criticized by some sections of the community. There is, accordingly, a considerable desire amongst farmers for an antibiotic substance which will leave the desired growth-promoting effect but which will leave no or no significant residues in animal products.
In U.S. patent application Ser. No. 627,439, filed July 3rd 1984, which issued as U.S. Pat. No. 4,557,933, on Dec. 10, 1985 , assigned to the present assignees, there is disclosed an antibiotic, there referred to as "chloropolysporin", which was isolated from the culture medium of a microorganism identified as Micropolyspora sp. SANK 60983.
We have now discovered that the same microorganism, and hence others of the genus Micropolyspora, produces a further two new antibiotic substances that are highly effective against gram-positive bacteria and that show considerable promise for use as growth-promoting agents in animals. It is believed that these substances may have been present in the chloropolysporin of the prior Application.